Production of nitriles



Patented Oct. 5,,

'PRODUCTION OF NITRILES Milton M. Marisic, Northfleld, Ill., and William I. Denton, Woodbury, and Richard B. Bishop, Haddonfleld, N. J assignors to Socony-Vacuum Oil Company, Incorporated, a corporation of New York No Drawing. Application March 26, 1947,

Serial No. 737,425

6 Claims. (Cl. 260-465) This invention relates to a process for produc ing nitriles having at least twocarbon-atoms per molecule, and is more particularly concerned with a catalytic process for producing nitriles having at least two carbon atoms per molecule, from cyclopa-rafiinic hydrocarbons.

Nitriles are organic compounds containing combined nitrogen. Their formula may be represented thus: R-CEN, in which R is an alkyl or an aryl group. These compounds are very useful since they can be converted readily to many valuable products such as acids, amines, aldehydes, esters, etc. 7

As is well known to those familiar with the art, several processes have been proposed for the preparation of nitriles. In general, however, all of these processes have been disadvantageous from one or more standpoints, namely, the relatively high cost of the reactants employed and/or the toxic nature of some of the reactants and/or the number of operations involved in their ultimate preparation. For example, aliphatic nitriles have been synthesized by oxidizing hydrocarbons to acids followed by reacting the acids thus obtained with ammonia in the presence of silica gel. Other methods involve reacting alkyl halides with alkali cyanides, reacting ketones with hydrogen cyanide in the presence of dehydration catalysts, etc. Aromatic nitriles have been synthesized by reacting alkali cyanides with aromatic sulfonates or with aromatic-substituted alkyl halides; by reacting more complex cyanides such as potassium cuprous cyanide, with diazonium halides; by reacting isothiocyanates with copper or with zinc dust; and by reacting aryl aldoximes with acyl halides.

We have now found a process for producing nitriles containing at least two carbon atoms, which is simple and inexpensive, and which employs non-toxic reactants.

We have discovered that nitriles containing at least two carbon atoms, can be prepared by reacting cycloparafilnic hydrocarbons with ammonia, at elevated temperatures, in the presence of certain catalysts of the type defined hereinafter.

Our invention is to be distinguished from the conventional processes for the production of hydrogen cyanide wherein carbon compounds, such as carbon monoxide, methane, and benzene, are reacted with ammonia at elevated temperatures in the presence of alumina, nickel, quartaclays, oxides of thorium and cerium, copper, iron oxide, silver, iron, cobalt, chromium, aluminum phosphate, etc. The process of the present invention 2 is also to be distinguished from the processes of the prior art for the production of amines wherein hydrocarbons are reacted with ammonia at high temperatures, or at lower temperatures in the presence of nickel; v

Accordingly, it is an object of the present invention to provide a process for the production of nitriles containing at least two carbonatoms per molecule. Another object is to aiford a catalytic process for the production ofv nitriles containing at least two carbon atoms. An important object is to provide a process for producing nitriles containing at least two carbon atoms which is inexpensive and commercially feasible. A specific object is to provide a process for producing nitriles containing at least two carbon atoms, from cycloperatures, in the presence of catalytic .materialobtained by decomposing a heteropoly acid or a salt of a heteropoly acid containing an element selected from the group consisting of molybdenum, tungsten and vanadium,

The cycloparafiinic hydrocarbons which are suitable as the hydrocarbon'reactant in the process of our invention are cyclopropanef cyclobutane; cyclopentane; and the-alkyl-substituted cyclopropanes, cyclobutanes and oyclopentanes;

the alkyl -substituted cyclohexanes; and the alkylsubstituted decalins. 0f the alkyl-substituted cycloparafilnic hydrocarbons, we prefer use the methyl-substituted cycloparaflinic hydrocarbons, and of these, dimethyl cyclohexane, methyl cyclohexane and methyl decalin are especially preferred. It will be clear from the discussion of reaction temperatures set forth hereinafter, that many of the aforementioned cycloparaffinic hydrocarbons are not present per se when in contact with ammonia anda catalyst of the type used herein, for many of them are cracked to related hydrocarbons under such conditions. Nevertheless, all the aforementioned cycloparaffinic hydrocarbons and their hydrocarbon decomposition products, which are in the vapor I phase under the herein-defined reaction conditions, serve the purpose of the presentinvention. It is to be understood also, that hydrocarbon mixtures containing one or more of the aforementioned cycloparafllnic hydrocarbons may also be used herein, and that when such mixtures are used the reaction conditions, such as contact time, will be slightly diflerent in view of the dilution effect of the constituents present with the said cycloparafilnic hydrocarbon or hydrocarbons. Accordingly, any of the aforementioned cycloparafilnic hydrocarbons, mixtures thereof, and hydrocarbon mixtures containing one or more of said cycloparaflinic hydrocarbons may be used.

The proportions of reactants, i. e., cycloparaffinic hydrocarbon and ammonia, used in our process may be varied over a wide range with little effect on the conversion per pass and ultimate yield. In general, the charge of reactants may contain as little as 2 mol. percent or as much as 98 mol. percent of cycloparafiinic hydrocarbon benefits of catalysts prepared from an interreactant. In practice, however, we use charges I containing between about mol. percent and about 90 mol. percent of cycloparaillnic hydrocarbon, and ordinarily, we prefer to use charges contalning a molar excess of ammonia over the cycloparafflnic hydrocarbon reactant.

As stated hereinbefore, we have found that the catalysts to be used to produce nitriles containing at least two carbon atoms per molecule, by reacting the aforementioned cycloparafllnic hydrocarbons with ammonia are those obtained by decomposing thermally heteropoly acids and salts of heteropoly acids, containing an element selected from the group consisting of molybdenum, tungsten and vanadium.

Heteropoly acids are well known in the literature (Modern Aspects of Inorganic Chemistry, II. J. Emelus and J. S. Anderson, New York, 1940, chapter V). The heteropoly acids operative in the process of the present invention are those which contain an acid anhydride molecule selected from the group consisting of M003, W0; and V205, and at least one other acid anhydridetype molecule, the latter being regarded as the central group of the acid. These heteropoly acids may also be defined broadly as those acids formed by the union of a radical of molybdic, tungstic or vanadic acidsor two or more of these radicals-with one or more radicals of other fairly strong acids or with amphoteric metal hydroxides. A typical heteropoly acid is phosphomolybdic acid, 1. e., H3[PO4(M0O3) 1213:1120, in which 2: represents the number of molecules of water associated with the crystalline acid and is generally a whole number, five to twenty-nine, wherein the phosphate group (P04) is the central group. Other representative acids which may be mentioned by way of non-limiting examples, are silico-molybdic acid, 1. e.,

H4[SlO4(M0O:) 12112320 and phosphovanadotungstic acid, i. e.,

Hz [304 (V205) ziWOa) a] .JJHaO Salts of the heteropoly acids referred to, which also are well known in the art, are likewise suitable for the preparation .of the catalysts of the process of the present invention. Typical salts of the heteropoly acids are ammonium silicomolybdate, i. e., (NH4)4[SiO4(M0Oa) 121-3ZH20, and nickel silicomoiybdate, i, e.,

N12 [SiO4(MOOa) 1a] .mHaO

These are'mentioned by way of non-limiting examples.

In the interest of brevity, the heteropoly acids and the salts of heteropoly acids contemplated mediate heteropoly compound are obtained.

Accordingly, the catalytic materials of the present invention may be obtained by thermally decomposing a heteropoly compound, 1. e., a heteropoly acid or a salt of a heteropoly acid, under the hereinafter defined conditions. In general, the temperatures to be used for effecting the thermal decomposition I of the heteropoly compounds depend upon the period of time during which a heteropoly compound is subjected to a given temperature. The object of the thermal treatment of the heteropoly compounds is to dehydrate and to decompose them to produce catalytic oxides and'yet avoid unnecessary sintering of the resultant catalytic oxides. Sintering detracts from the catalytic activity of the resultant catalytic oxides by reducing the surface area thereof. Accordingly, to obtain the most active catalysts, the thermal treatment of the heteropoly compounds must be carried out at a temperature and for a period of time suflicient to decompose a heteropoly compound, while maintain a minimum. In practice, we have found that treatment of the heteropoly compounds at temperatures varying between about 300 F. and about 950 F., for periods of time varying between about two hours and about ten hours, are most convenient from the standpoint of commercial manufacture of the catalysts to be used in the process of this invention, It must be clearly understood, however, that higher or lower temperatures may be used, provided that at higher temperatures, relatively short periods of time are employed so that sintering of the resultant catalytic oxides is kept at a minimum, and that at lower temperatures, relatively longer periods of time are employed to ensure decomposition of the heteropoly compounds.

While the decomposition products of the heteropoly compounds exhibit'an appreciable degree of catalytic efiectiveness when used per se, they generally possess additional activity when used in conjunction with the well known catalyst supports, such as activated alumina, bauxite, silica gel, carborundum, pumice, clays and the like. We especially prefer to use activated alumina (A1203) as a catalyst support. Without any intent of limiting the scope of the present invention, it is suspected that the enhanced catalytic activity of the supported catalysts is attributable primarily to their relatively large surface area.

The concentration of catalytic heteropoly compound in the supported catalysts influences the conversion per pass. In general, the conversion per pass increases with increase in the concentration of heteropoly compound. For example, we have found that a catalyst comprising initially 20 parts by weight of phosphomolybdic acid on parts by weight of activated alumina is more effective than one comprising initially 10 parts by weight of phosphomolybdic acid on parts by weight of activated alumina. It is to be underaccacra stood, however, that supported catalysts containing larger or smaller amounts of catalytic heteropoiy compound may be used in our process.

The catalysts of the present invention possess several advantages. In addition to providing relatively high conversions of the aforementioned further operation becomes uneconomical or disadvantageous from .a practical standpoint, the

catalyst may be regenerated as is well known in the art, by subjecting the same to a careful oxidation treatment, for example, by passing a stream of air or air diluted with flue gases over the catalyst under appropriate temperature conditions and for a suitable period of time, such as the same period of time as the catalytic operation. Preferably, the oxidation treatment is-followed by a pur'ging treatment, such as passing over the catalyst a stream of purge gas, for example, nitrogen, carbon dioxide. steam, etc.

The lower oxides of the aforesaid heteropoiy compounds, obtained by decomposing thermally the latter, are not volatile under conditions generally employed in oxidatlve catalyst regeneration. Therefore, it will be apparent that these catalysts will have a long useful life. The volatility of the catalysts used herein can be correlated with their color. Thus, phosphomolybdic acid (or ammonium phosphomolybdate) on decomposition yields a product which is dark blue in color and non-volatile; whereas arsenomolybdic acid decomposes to a product which is faint blue in color and which is slightly volatile at elevated temperatures in a current of air. Decomposition of silico-molybdic acid results in a product which Exmu 2 Decomposition product of ammonium phos-v phovanadotungstate on activated alumina Two hundred (200) grams of ammonium tungstate, (N114) :WOi, 43.4 grams of ammonium metavanadate, .NHiVOi, 8.6 grams of ammonium monohydrogen phosphate (Nikki-IP04, and 140 c. c. of 36% aqueous ammonia were added to '3 liters of distilled water. The mixture was stirred and heated to a temperature 01 about 200 F. until solution of the salts was complete. The volume was kept constant by occasionally adding distilled water. A deep red solution was obtained. The solution was evaporated to about 500 c. c. and then was poured onto 500 c. c. of activated alumina (8-14 mesh granules). Water was removed by evaporation and the impregnated alumina thus obtained was gradually heated to a temperature of 840 F. and maintained at that temperature for two hours. The catalytic material thus formed was reddish brown in color and comprised oxides of vanadium, tungsten and phosphorus on alumina. It may be considered as phosphovanadotungsticacid.

EXAMPLE 3 Decomposition product of silicomolybdic acid on activated alumina derived from time during which a unitvolume of the reactants is intermediate in color and volatility to those of the catalytic products obtained from phosphomolybdic acid and arsenomolybdic acid.

Illustrative of the catalystscontemplated for use in the process of the present invention are the following:

EXAMPLE 1 Decomposition product of phosphomolybdic acid on activated alumigta Two hundred (200) c. c. of 36% hydrochloric acid were added to 600 c. c of a solution containing 400 grams of sodium molybdate,

NazMoO .2H20

with constant stirring. The resulting solution was maintained at a temperature of 170 F. and

400 c. c. of a solution containing 98.6 grams of sodium monohydrogen phosphate,

Na I-lPO .12I-1z0 were added thereto, followed by 4222 c. c. of 38% hydrochloric acid, the latterbeing added dropwise gradually heated to a temperature of 840 F. and

maintained at that temperature for two hours.

is in contact with a unit volume of catalyst, may vary betweena fraction of a second and several minutes. Thus, the contact time may be as low as 0.01 second and as high as 20 minutes. We prefer to use contact times varying between about 0.1 second and about one minute, and more particularly, contact times varying between about 0.3 second and about 30 seconds.

In general, the temperatures to be used in our process vary between about 850 F. and up to the decomposition temperature of ammonia (about 1250-1300" F.), and preferablyybetween about 925 F. and about 1075 F. The preferred temperature to-be used in any particular operation will depend upon the natureof the cycloparaffinic hydrocarbon reactant used and-upon the type of catalyst employed. Generally speaking, the higher temperatures increase the conversion per pass, but they also increase the decompositioning chamber.

the catalyst fiows concurrently, or countercur- Bubatmospheric pressures appear to favor the reactions involved since the reactionproducts have a larger volume than the reactants, andand present increased difficulties in recycling unreacted charge materials. Therefore, atmospheric pressure or superatmospheric pressures are preferred. I

At the present time, the reaction mechanism involved in the process of the present invention is not fully understood. Fundamentally, the simplest possible method of making nitriles is to introduce nitrogen directly into the hydrocarbon reactant molecule, thereby avoiding intermediate steps with their accompanying increased cost. In our process, we have noted that considerable amounts of hydrogen are evolved, and that aliphatic nitriles as well as aromatic nitriles are formed. Hence, it is postulated, without any intent of limiting the scope of the present invention, that in our process, the aliphatic nitriles are formed by an initial ring opening followed by replacement of hydrogen with nitrogen, while the aromatic nitriles are formed by the dehydrogenation of a cycloparailinic hydrocarbon reactant to form an aromatic hydrocarbon, followed by introduction of nitrogen therein.

The present process may be carried out by making use of any of the well-known techniques for operating catalytic reactions in the vapor phase effectively. By way of illustration, methyl cyclohexane and ammonia maybe brought-together in suitable proportions and the mixture vaporized in a preheating zone. The vaporized mixture is then introduced into a. reaction zone containing a catalyst of the type defined hereinbefore. The reaction zone may be a chamber of anysuitabletype useful in contact-catalytic operations; for example, a catalytst bed contained in a shell, or a, shell through which the catalyst flows concurrently, or countercurrently, with the reactants. The vapors of the reactants are maintained in contact with the catalyst at a predetermined elevatedtemperature and for a predetermined period of time, both as set forth here- 'inbefore, and the resulting reaction mixture is passed through a condensing zone into a receiv- It will be understood that when rently, with the reactants in a reaction chamber,

the catalyst will be thereafter suitably separated from the reaction mixture by filtration and purging, etc. The reaction mixture will be predominantly a mixture of nitriles, hydrogen, toluene, unchanged methyl cyclohexane, and unchanged ammonia. The nitriles, toluene, and the unchanged methyl cyclohexane will be condensed in passing through the condensing zone and will be retained in the receiving chamber. The nitriles can be separated from the unchanged methyl cyclohexane and toluene by any of the numerousand well known separation procedures, such as fractional distillation. Similarly, the uncondensed hydrogen and unchanged ammonia can be separated from each other. The unchanged methyl cyclohexane and ammonia (and toluene, if desired) can be recycled, with or without fresh methyl cyclohexane and ammonia, to the process.

It will be apparent that the process may be operated as a batch or discontinuous process as by using a catalyst-bed-type reaction chamber in which the catalytic and regeneration opera tions alternate. With a series of such reaction chambers, it will be seen that as the catalytic operation is taking place in one or more of the reaction chambers, regeneration of the catalyst will be taking place in one or more of the other reaction chambers. correspondingly, the process may be continuous when we use one or more catalyst chambers through which the catalyst flows in contact with the reactants. In such a continuous process, the catalyst will fiow through the reaction zone in contact with the reactants and will thereafter be separated from the reaction mixture as, for example, by accumulating the catalyst on a suitable filter medium, or by isolating finely divided catalyst in powder form by means of cyclone separators, before condensing the reaction mixture. In a continuous process, therefore, the catalyst-fresh or regenerated,

and thereebtants-fresh or recycle, will continu ously flow through a reaction chamber.

. catalyst chamber heated by circulating a heattransfer medium outside the shell, and containing parts by weight of a ctalyst prepared in accordance with Example 1 was used. Ammonia and methyl cyclohexane in a molar ratio of 2:1, respectively, were introduced in the vapor phase into the reactor. The reaction temperature and the contact time were 1050 F. and 4 seconds, respectively. The reaction mixture was passed from the reactor, through a condenser, into a first receiving chamber. Hydrogen and unchanged ammonia were collected in a second receiving chamber and then separated from each other. The nitriles remained in the first receiving chamber and were subsequently separated by distillation. Small amounts of the methyl cyclohexane were converted to acetonitrile, and about 1% by weight per pass, was converted to benzonitrile.

It will be apparent that the present invention provides an efiicient, inexpensive and safe process for obtaining nitriles. Our process is of considerable value in making available relatively inexpensive nitriles which are useful, for example, as intermediates in organic synthesis.

This application is a continuation-in-part of copending application, Serial Number 539,034, filed June 6. 1944, now abandoned.

Although the present invention has been described in conjunction with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Such variations and modifications are considered to be within the purview and scope of the appended claims.

We claim:

1. A process for the production of nitriles having at least two carbon atoms per molecule, which, comprises contacting a cycloparaflinic hydrocarbon selected from the group consisting of methyl cyclohexane, dimethyl cyclohexane, and methyl decalin, with ammonia, in gaseous phase, at temperatures .falling within the range varying between about 925 F. and about 1075 F., in the presence of catalytic oxides obtained by treating a heteropoly compound containing the acid anhydride molecule M003, at a temperature and ior a period of time sufficient to decompose said heteropoly compound.

2. A process for the production of nitriles having at least two carbon atoms per molecule, which comprises contacting a cycloparafllnic hydrocar- 3. A process for the production of nitriles hav-' ing at least two carbon atoms per molecule, which comprises contacting a cycloparamnic hydrocarbon selected from the group consisting of methyl cyclohexane, dimethyl cyclohexane, and methyl deca-lin, with ammonia, in gaseous phase, at temperatures falling within the range varying between about 925 F. and about 1075 F-., in the presence of catalytic oxides obtained by treating a heteropoly compound containing the acid anhydride molecule M001, at a temperature falling within the range varying between about 300 F. and about 950 F. and for a period of time fallin within the range varying between about two hours and ten hours, supported on alumina.

4. A process for the production of nitriles having at least two carbon atoms per molecule, which comprises contacting methyl cyclohexane with ammonia, ingaseous phase, at temperatures falling within the range varying between about 925 10 1 and about 1075 F.. in the presence of catalytic oxides obtained by treating a heteropoly com pound containing the acid anhydride molecule M003, at a temperature and for a period or time sufllcient to decompose said heteropoly compound. V

5. A process for the production of nitriles having at least two carbon atoms per molecule, which comprises contacting methyl cyclohexane with ammonia, in gaseous phase, at temperatures falling within the range varying between about 925 F. and about 1075 F., in the presence of catalytic oxides obtained by treating a heteropoly compound containing the acid anhydride molecule M003, at a temperature falling within the range varying between about 300 F. and about-950 F.

and for a period of time falling within the range varying between about two hours and ten hours,-

supported on a catalyst support.

6. A process for the production of nitriles having at least two carbon atoms per molecule, which comprises contacting methyl cyclohexane with ammonia, in gaseous phase, at temperatures falling within the range varying between about 925 F. and about 1075 F., in the presence of catalytic oxides obtained by treating a heteropoly compound containing the acid anhydride molecule Moos, at a temperature falling within the range varying between about 300 F. and about 950 F. and for a period of time falling within the range varying between'about two hours and ten hours, supported on alumina.

. MILTON. M. MARISIC. WILLIAM I. BENTON.

RICHARD B. BISHOP.

REFERENCES crrnn The following references are of record in the file oithis patent: 

